Electronic switch



Get. 4 1949.

Filed May 13. 1947 T. H. CLARK 2,483,400

ELECTRONIC SWITCH 2 Sheets-Sheet l FIG. l

gwoon/tow aum/wry T. H. CLARK ELECTRONIC SWITCH 2 Sheets-Sheet 2 Oct. 4,1949.

Filed May 13, 1947 F/GZ.

LINE FINDER IIA/rf Patented Oct. 4, 1949 ELECTRONIC SWITCH Trevor H.Clark, Boonton, N. J., assignor to International Standard ElectricCorporation, New York, N. Y., a corporation of Delaware Application May13, 1947, Serial No. 747,873 In France May 26, 1939 Section 1, PublicLaw 690, August 8, 1946 Patent expires May 26, 1959 6 Claims.

The present invention relates to control or switching devices employingelectronic apparatus.

In automatic telephone or remote control systems, etc. devices areemployed registering the signals transmitted by the operator or by theuser. In numerous cases this is obtained by means of mechanicalswitches, for example, the so-called step-by-step switches which receivethe impulses generated by a dial or by a remote control device,translate them, and control various members carrying out the desiredoperations.

This mechanical execution has the drawback of being relatively slow inoperation, and moreover, the mechanical parts wear and require regularsupervision and replacement of parts.

One of the objects of the present invention is the provision of animproved switch, particularly one which performs the function of themechanical step-by-step switch and which preferably has otherfeaturessuch as being capable of operation at high speed requiring no periodicimpulses, and lessening the requirement for replacement of parts.

The above-mentioned and other features and objects of this inventionwill become more apparent and the invention itself though notnecessarily dened by said features and objects will be best understoodby reference to the following description of an embodiment of theinvention taken in connection with the accompanying drawings, Whereim.

Fig. 1 is a schematic diagram of a switching arrangement embodying thepresent invention as applied to an automatic telephone system; and

Fig. 2 is a schematic diagram of a modication of a portion thereof.

The embodiment shown is the application of the invention to an automatictelephone system, but it is clear that the invention is not restrictedto such an automatic telephone system, and may be applied to any remotecontrol system employing current or voltage impulses as a means ofconnection between the control stations and the controlled apparatus.

Referring to Figure 1, the index I represents an impulse generatingdevice, this impulse generator may be a telephone dial or any otherarrangement producingvimpulses of such a character that they cause therelay 2 to operate.

The relay 2 is actuated by the impulse transmittiug system when thecircuit comprising the battery 3, the relay 2, and the dial I is closed.In

the non-actuated or normal position the armature 4 of the relay 2 closesa circuit comprising the battery 9, the contact 5, the armature 4, theresistance 8 and the condenser 'I.

The resistance 8 is chosen suiliciently high to avoid the formation ofsparks on the contacts, and yet suciently low for the condenser I to becharged at the potential of the battery 9 in a. short `time with respectto the time during which the circuit remains closed. When the relay 2 isactuated the circuit composed by the condenser 1, the resistance 8, thecontacts 4 and 6, the condenser Ill and the deflecting plate I2, of thecathode ray tube II is closed. These circuits are well known both withregard to their construction and their operation.

It will only be recalled here that the potential onthe terminals of thecondenser I0 will be given by:

E|=N;+1 for the rst impulse where E1 is the resultant potential on theterminals of the condenser I0, N is the ratio between the capacities ofthe condenser I0 and of the condenser 1, e is the potential ofthebattery 9:

E2-E12-N11 for the second impulse E.. -e[(`% gie-*1)-I-] for the nthimpulse electron gun I4 generating electronic beams, de-

ecting plates I2 and I3 and a system of target or electron receivingelectrodes I 6 to 26. The

feed potentials of this tube are supplied by the rectified and filteredA. C. feed system I5. It is clear that the number of receivingelectrodes may be increased or decreased as required.

The electronic beam generatedby the system I 4 is initially directed soas to be received by the electrode I6 when the potential on theterminals of the condenser i0 is zero. The remainder of the electrodesII to 26 are arranged so that the electronic beam progresses from one tothe other in succession. The deflection of the cathodic beam being inproportion to the potential on the terminals of the condenser I0, if animpulse has been received the beam vwill arrive on the electrode I1, iftwo impulses have been received the beam will arrive on the electrodeI8, etc. and ii' 10 impulses have been received the beam will strike theelectrode 28. The electrodes are dimensioned and arranged in accordancewith the formula given above. The electronic current arrives on theearth or ground terminal which is the positive terminal of the source ofsupply, across one of the resistances 21 and consequently creates apotential dilerence across the terminals of that resistance which itpasses through.

At 28 are shown diagrammatically 10 terminals of a mechanical switch,for example, of the well known clutch type, much used in the rotaryautomatic telephone systems and known by the name of line nder. Theclutch or driving mechanism of this switch is shown at 39. The contact40 and the armature 38 are closed during the operation of the linefinder, that is to say while the contacts 28 are searched by the brushI42, the .A

clutch being supplied with the power from source 4|. At the moment whenthe circuit of the armature 38 is opened the brush 42 stops.

When the circuit formed by one of the resistances 21, the corrspondingcontact 28, the contact of the brush 42 and the resistance 29 is closed,a part of the current of the electronic beam will circulate in theresistance 29 and a potential will appear on the terminals o thisresistance, the earthed end being positive. This difference of potentialwill be applied to the grid of an amplifier valve 30 which may be avalve of any type but preferably of the pentode type as shown in thedrawing and in which the plate current is not zero when the gridpotential is zero.

The resistances 21 and 29 are of such a valuel that when current ilowsthrough resistor 29, the resulting potential applied to the grid of thevalve 30 decreases the plate current of Valve 30 to zero or around zero.The resistance 29 may be chosen lower than the resistance 21, so thatanother line finder operating in parallel with the one illustrated inthe drawings cannot stop on the same contact.

The plate current of the valve 30 passing across resistance 3|, createsa diierence of potential between the terminals of this resistance. Thispotential which is applied between the cathode and the grid oi thesecond valve 32, is polarised, in such a way that the grid becomesnegative with regard to the cathode during the passage of the current,and of such an amplitude that the plate current of the valve 32 isreduced to zero. However, when no current traverses the resistance 3|,the control grid of the valve 32 is at the potential of the cathode anda strong current circulates in the plate circuit. This current goesthrough the winding 34 of the relay 33, a second current goes throughthe Winding 35 of the same relay, and this current is regulated by meansof the resistance 43, in such a way that the armature of the relay isattracted when no current circulates in the winding 34. The windings arearranged and connected in such a way that when they are carrying normalcurrents, the magnetic forces are opposed. Even a very weak currentthrough the winding 34 causes the relay to overbalance and close thecontacts 36.

When the contacts 3G close the relay 31 is then actuated and the circuitopened. This interrupts the current in the clutch 39 and the finder isstopped. The whole of the operation takes place so rapidly that thecontact of the brush 42 is stopped near the centre of the contact 28corresponding to the receiving electrode of the tube Il on which theelectron beam rests.

It should be noted that the sweeping of the beam across various targetsproduces transient currents through resistors 21 of such small valuethat, if brush 42 is on the corresponding contact of the resistor 21through which said small current is flowing, the resultant current nowthrough resistor 29 is insuicient to cause tube 38 to be blocked andthereby operate the system. When, however, the beam comes to rest on oneof the targets and the line iinder brush 42 touches the correspondingcontact the resulting current through resistor 29 causes tube 30 to beblocked which in turn causes tube 32 to conduct whereby current flowsthrough winding 34 closing contact 36 and energizing relay 31 whichdraws armature 38 from contact 48 and stops the line nder clutch 39.

The relay 33 is a relay with quick release quickly closing contacts andslow operation slowly opening contacts so that the line finder ismaintained in position even if the contact 42-28 is momentarily brokenor if the potential on the terminals of the resistance 29 momentarilyfalls below the value necessary to maintain at zero the plate current ofthe valve 30.

The potentials necessary for the operation of thevalves 30 and 32 aresupplied by the source of supply 45 which may be a part of the currentsupply system l5.

The bias current of the relay 33 passing through the winding 35 isreduced to zero, when the relay 31 operates since the armature 38 makescontact with the contacts 44 and short circuits the winding 35. ndercannot operate before the bias current of the relay 31 has been cut off.

Figure 2 represents a modification of the system described in Figure 1in which the brush 42 is directly connected in the grid circuit of thesecond valve 32 and in which only the relay 31 is utilised.

Tube 32 is normally conductive causing current to flow through relay 31and armature 38 to touch contact 40 thereby supplying energy to theclutch 39 and causing the brush 42 to continuously and cyclically sweepthe contacts 28. When the brush 42 touches the contact 28V connected tothe target electrode on which the beam is resting, current will owthrough brush 42 and resistance 29. The potential across resistance 29blocks tube 32 deenergizing relay 31 whereupon the armature 38 swingsaway from contact 40 deenergizing clutch 39 and holding the line finder;with brush 42 resting on its proper contact.

The speed of operation of the circuit of Figure 2 will be slightlygreater than that of the arrangement on Figure 1, in view of the factthat it is possible to obtain a greater speed of operation for a singlerelay than for two relays in series. A relay can be connected inparallel with the clutch 39 so that the clutch circuit cannot beactuated again.

While I have described above the principles of my invention inconnection with specic apparatus, and particular modifications thereof,it is to be clearly understood that this description is made only by wayof example and not as a limitation on the score of my invention.

What is claimed is:

1. A control arrangement comprising a cathode ray tube including beamforming means, beam deflecting means. and a plurality of targetelectrodes arranged so that the particular elec- This insures properoperation as the v trode impinged upon by the beam is determined by thebeam deiiection, means for producing a selected number of pulses, meanscontrolling the beam deiiecting means and responsive to said pulses fordefiecting the beam to a degree determined by the number of pulses, aline nder including a movable brush, a plurality of contacts eachconnected to a separate one of said electrodes and adapted to pass aportion of the electron beam current impinging upon said electrode tosaid movable brush, a driving mechanism for moving said brush over saidcontacts successively and means responsive to the ow of current from oneof said contacts through said brush for deenergizing said drivingmechanism to thereby halt said brush.

2. A control arrangement according to claim 1 wherein said controllingmeans includes a condenser and means for applying the pulses to saidcondenser to charge it to a level determined4 by the number of saidpulses, andmeans for applying the charge on said condenser to the beamcontrolling means.

3. A control arrangement according to claim 2 wherein said beam deectingmeans comprises electrostatic plates to which the charge on saidcondenser is applied.

4. A control arrangement according to claim 2 wherein the pulseproducing means includes a source of pulses, a. relay actuated by eachone of said pulses and having contacts, a second condenser arranged tobe charged through said contacts when the relay is in deenergizedcondition and arranged to distribute part of its stored energy to themst-mentioned condenser through said contacts when the relay isenergized.

5. A control arrangement according to claim 1 wherein the deenergizingmeans includes a. normally conductive electron tube, a relay arranged inthe output circuit thereof and energized by current flowing through saidtube, a source of power for said driving mechanism, and a set ofcontacts, forming part of the relay, in series between said source oipower and said driving mechanism and arranged to be closed while saidrelay is energized.

6. A control arrangement according -to claim 1 wherein said deenergizingmeans includes a first relay adapted upon energization thereof to openthe circuit energizing said driving mechanism, a second relay having itscontacts in series in the circuit supplying energy to said rst relay,said second relay having a first winding normally connected to havecurrent flow therethrough to thereby maintain its associated contacts inopen position, and a second winding, and means responsive to the iiow ofcurrent through the movable brush for producing a current iiow throughsaid second winding in a direction opposite the current flow of the irstwinding whereby the contacts of said second relay close, therebyenergizing said first relay and deenergizing the driving mechanism.-

TREVOR H. CLARK.

REFERENCES CITED Great Britain -..'May 24, 1938

